The number of screening techniques for inspecting cargo and luggage, principally for reasons of security, has increased in recent times. One recently proposed technique, for example, is disclosed in EP 1579202, and comprises a sealed-tube or similar generator for producing substantially mono-energetic fast neutrons produced via the D-T or D-D reactions, a source of X-rays or gamma-rays for penetrating an object, a collimating block surrounding the neutron and gamma-ray sources, apart from slots for emitting fan-shaped radiation beams, and a detector array.
One existing system employs a pulsed-neutron elemental analysis detector, and allows the screening of a sample or object—such as whether it comprises or contains an explosive—after a data collection period of about 10 minutes. While this may be acceptable for screening a small number of items, it becomes prohibitive for large quantities of cargo.
Such techniques may be employed to screen a truck, and in such cases are provided in the form of a screening portal in which the truck is parked. Port Technology International (published by Maritime Information Services Ltd) published a cost-benefit analysis of cargo screening in September 2006, which demonstrated that, assuming a fixed-site cargo screening station operating at 20 containers/h, the equipment related costs of screening were US$23.49 per container.